Electric charge, Coulomb’s law, electric field

Electric Charge

1. Electric charge is a fundamental property of matter that causes it to experience a force in an electric field.
2. There are two types of charges: positive and negative.
3. Like charges repel each other, and unlike charges attract each other.
4. Charge is measured in coulombs (C).
5. Quantization of charge states that charge exists in discrete packets, as multiples of the elementary charge e (1.6 × 10^-19 C).
6. Conservation of charge states that the total charge in an isolated system remains constant.

Coulomb’s Law

1. Coulomb’s law gives the force between two point charges: \( F = k \frac{q_1 q_2}{r^2} \).
2. The force is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.
3. The constant k is the Coulomb’s constant, \( k = \frac{1}{4 \pi \epsilon_0} \).
4. ε₀ is the permittivity of free space, \( \epsilon_0 = 8.854 × 10^{-12} \, \text{F/m} \).
5. Coulomb’s law applies in vacuum and for point charges.
6. The force acts along the line joining the charges and is a central force.

Electric Field

1. An electric field is a region around a charge where other charges experience a force.
2. The electric field is represented by the symbol E and is a vector quantity.
3. The electric field due to a point charge is \( E = k \frac{q}{r^2} \).
4. The direction of the field is away from a positive charge and toward a negative charge.
5. The unit of electric field is newton per coulomb (N/C) or volt per meter (V/m).
6. The electric field lines indicate the strength and direction of the field. Closer lines represent a stronger field.
7. The electric dipole consists of two equal and opposite charges separated by a distance, creating a unique field pattern.

Key Principles

1. Superposition principle: The net electric field at a point is the vector sum of electric fields due to all charges.
2. Gauss’s law: The total electric flux through a closed surface is proportional to the enclosed charge.
3. The relationship between electric force and electric field is \( F = qE \), where \( F \) is the force on charge \( q \).

Applications

1. Coulomb’s law is used to calculate forces in atomic and molecular interactions.
2. Electric fields are crucial in designing capacitors and electrostatic devices.
3. The principles are used in particle accelerators to manipulate charged particles.
4. Understanding electric fields helps in shielding sensitive devices from electrostatic interference.
5. Electric dipoles play a role in polar molecules and their interactions.